Non toxic, antibacterial, biodegradable hydrogels with pH-stimuli sensitivity: Investigation of swelling parameters

Transparent Oil-Water Separating Hydrophobic Sponge Prepared from a Pickering High Internal Phase Emulsion Stabilized by Octadecyltrichlorosilane Grafting Carbon Nanotubes

Increasingly, oil spills and industrial discharges are wreaking havoc on the water environment; in order to efficiently separate oil and water from sewage containing oil or organic solvents, a novel porous polymer (P(EHA-co-BA)) was prepared by Pickering high internal phase emulsion (HIPE) template method. To obtain polyHIPE with better oil/water separation capacities, octadecyltrichlorosilane (OTS)-modified carbon nanotubes (CNTs) and surfactants were used as costabilizers for HIPE, which improved the stability of HIPE as well as the mechanical properties and the separation efficiency of polyHIPE. In the presence of 1 wt % OTS-CNT adding in the oil phase, 1%OTS-CNT polyHIPE has high porosity (92.21%), favorable hydrophobicity (a water contact angle of 128°), and excellent mechanical properties. As a result, 1%OTS-CNT polyHIPE has high absorption of oils and oily solvents, e.g., dichloromethane up to 36 g/g, and maintains an absorption efficiency of >97% after 20 reapplications. In the formulation of polyHIPE, cinnamaldehyde (CA) has been added to provide superior antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). It appears that the novel polyHIPE proposed in this work is a reusable antibacterial porous polymer with promising applications for oil-water separation.

Thermal, morphology and bacterial analysis of pH-responsive sodium carboxyl methylcellulose/ fumaric acid/ acrylamide nanocomposite hydrogels: Synthesis and characterization

In this present investigation, sodium carboxymethyl cellulose grafted with Fumaric acid/Acrylamide (CMC/FA/AAm=CFA) hydrogel and their silver nanocomposite hydrogels (CFA-Ag x, x = 5, 10 and 20) were developed by simple, cost effective and ecofriendly greener method. Mint leaf extract was used as an efficient natural reducing agent due to presence of active and antioxidant potential of polyphenol and flavonoid components. Swelling equilibrium of CFA hydrogel showed Seq% 3000 both in pH medium and distilled water. CFA (90:10) hydrogel has been produced greater than Seq% 6000. The synthesized CFA (90:10)-Ag-5, CFA (90:10)-Ag-10 and CFA (90:10)-Ag-20 nanocomposite hydrogels have been observed lower Seq% 2000-3000 than the CFA hydrogel. The homogeneous distribution of AgNPs throughout the CFA hydrogel and nanocomposites has been explored by SEM analysis. The interaction of network heteroatoms with AgNPs has been strongly revealed by the FTIR spectra and XRD analysis. The thermal stability of CFA (90:10)-Ag-5, 10, and 20 nanocomposite hydrogels have showed greater stability than CFA hydrogel which is confirmed by TGA/DSC thermogram analysis. The TEM analysis was used to explore a uniform distribution of spherical AgNPs (10 nm-50 nm) embedded on the CFA composite hydrogel. The CFA (90:10)-Ag-20 nanocomposite hydrogel has showed good antibacterial activity beside E. coli (Gram positive) and S. aureus (Gram negative) pathogens. Based on the antibacterial activity and swelling properties of CFA-Ag nanocomposite hydrogels have the ability to accelerate the antibacterial activity and are potential candidates for medical and environmental applications.

pH-responsive scaffolds for tissue regeneration: In vivo performance

A myriad of pH-sensitive scaffolds has been reported in recent decades. Information on their behaviour in vitro under conditions that mimic the pH changes that occur during tissue regeneration is abundant. Differently, the in vivo demonstration of the advantages of pH-responsive systems in comparison with non-responders is more limited. The in vivo scenario is very complex and the intricate relationship between the host response, the overall pathological conditions of the patient, and the risk of colonization by microorganisms is very difficult to imitate in in vitro tests. This review aims to shed light on how the changes in pH between healthy and damaged states and also during the healing process have been exploited so far to develop polymer-based scaffolds that actively contribute in vivo to the healing process avoiding chronification. The main strategies so far tested to prepare pH-responsive scaffolds rely on (i) changes in ionization of natural polymers, ionizable monomers and clays, (ii) reversible cross-linkers, (iii) coatings, and (iv) production of CO2 gas. These strategies are analysed in detail in this review with the description of relevant examples of their performance on specific animal models. The versatility of the techniques used to prepare biocompatible and environment-friendly pH-responsive scaffolds that have been implemented in the last decade may pave the way for a successful translation to the clinic. STATEMENT OF SIGNIFICANCE: We report here on the most recent advances in pH-responsive polymer-based scaffolds that have been demonstrated in vivo to be suitable for wound and bone healing. pH is a critical variable in the tissue regeneration process, and small changes can speed up or completely stop the process. Although there is still a paucity of information on the performance in the complex in vivo environment, recently reported achievements using scaffolds endowed with pH-responsiveness through ionic natural polymers, ionizable monomers and clays, reversible cross-linkers, coatings, or formation of CO2 ensure a promising future towards clinical translation.

Instantaneous self-healing and strongly adhesive self-adaptive hyaluronic acid-based hydrogel for controlled drug release to promote tendon wound healing

The treatment of tendon injuries is an important healthcare challenge. Irregular wounds, hypocellularity, and prolonged inflammation impede the rate of healing for tendon injuries. To address these problems, a high-tenacity shape-adaptive, mussel-like hydrogel (PH/GMs@bFGF&PDA) was designed and constructed with polyvinyl alcohol (PVA) and hyaluronic acid grafted with phenylboronic acid (BA-HA) by encapsulating polydopamine and gelatin microspheres containing basic fibroblast growth factor (GMs@bFGF). The shape-adaptive PH/GMs@bFGF&PDA hydrogel can quickly adapt to irregular tendon wounds, and the strong adhesion (101.46 ± 10.88 kPa) can keep the hydrogel adhered to the wound at all times. In addition, the high tenacity and self-healing properties allow the hydrogel to move with the tendon without fracture. Additionally, even if fractured, it can quickly self-heal and continue to adhere to the tendon wound, while slowly releasing basic fibroblast growth factor during the inflammatory phase of the tendon repair process, promoting cell proliferation, migration and shortening the inflammatory phase. In acute tendon injury and chronic tendon injury models, PH/GMs@bFGF&PDA significantly alleviated inflammation and promoted collagen I secretion, enhancing wound healing through the synergistic effects of its shape-adaptive and high-adhesion properties.

Antibacterial smart hydrogels: New hope for infectious wound management

Millions of people die annually due to uncured wound infections. Healthcare systems incur high costs to treat wound infections. Tt is predicted to become more challenging due to the rise of multidrug-resistant conditions. During the last decades, smart antibacterial hydrogels could attract attention as a promising solution, especially for skin wound infections. These antibacterial hydrogels are termed 'smart' due to their response to specific physical and chemical environmental stimuli. To deliver different drugs to particular sites in a controlled manner, various types of crosslinking strategies are used in the manufacturing process. Smart hydrogels are designed to provide antimicrobial agents to the infected sites or are built from polymers with inherent disinfectant properties. This paper aims to critically review recent pre-clinical and clinical advances in using smart hydrogels against skin wound infections and propose the next best thing for future trends. For this purpose, an introduction to skin wound healing and disease is presented and intelligent hydrogels responding to different stimuli are introduced. Finally, the most promising investigations are discussed in their related sections. These studies can pave the way for producing new biomaterials with clinical applications.

Glucose and MMP-9 dual-responsive hydrogel with temperature sensitive self-adaptive shape and controlled drug release accelerates diabetic wound healing

Chronic diabetic wounds are an important healthcare challenge. High concentration glucose, high level of matrix metalloproteinase-9 (MMP-9), and long-term inflammation constitute the special wound environment of diabetic wounds. Tissue necrosis aggravates the formation of irregular wounds. All the above factors hinder the healing of chronic diabetic wounds. To solve these issues, a glucose and MMP-9 dual-response temperature-sensitive shape self-adaptive hydrogel (CBP/GMs@Cel&INS) was designed and constructed with polyvinyl alcohol (PVA) and chitosan grafted with phenylboric acid (CS-BA) by encapsulating insulin (INS) and gelatin microspheres containing celecoxib (GMs@Cel). Temperature-sensitive self-adaptive CBP/GMs@Cel&INS provides a new way to balance the fluid-like mobility (self-adapt to deep wounds quickly, approximately 37 °C) and solid-like elasticity (protect wounds against external forces, approximately 25 °C) of self-adaptive hydrogels, while simultaneously releasing insulin and celecoxib on-demand in the environment of high-level glucose and MMP-9. Moreover, CBP/GMs@Cel&INS exhibits remodeling and self-healing properties, enhanced adhesion strength (39.65 ± 6.58 kPa), down-regulates MMP-9, and promotes cell proliferation, migration, and glucose consumption. In diabetic full-thickness skin defect models, CBP/GMs@Cel&INS significantly alleviates inflammation and regulates the local high-level glucose and MMP-9 in the wounds, and promotes wound healing effectively through the synergistic effect of temperature-sensitive shape-adaptive character and the dual-responsive system.

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The hydrogel with temperature-sensitive adaptive shape can fill irregular wounds.

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The hydrogel on-demand releases drugs responding to diabetic wound environment.

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The hydrogel significantly accelerated diabetic wound healing.

Bioactivity of star-shaped polycaprolactone/chitosan composite hydrogels for biomaterials

Recently, our group reported the synthesis and fabrication of composite hydrogels of chitosan (CS) and star-shaped polycaprolactone (stPCL). The co-crosslink of modified stPCL with carboxyl at the end chain (stPCL-COOH) provided good mechanical properties and stability to the composite hydrogels. This research presents the bioactivities of composite hydrogels showing a potential candidate to develop biomaterials such as wound dressing and bone tissue engineering. The bioactivities were the antibacterial activity, cell viability, skin irritation, decomposability, and ability to attach ions for apatite nucleation. The results showed that all the composite hydrogels were completely decomposed within 2 days. The composite hydrogels had better antibacterial activity and higher efficiency to Gram-negative (Escherichia coli) than to Gram-positive (Staphylococcus epidermidis) bacteria. The composite hydrogels were studied for cell viability based on MTT assay and skin irritation on rabbit skin. The results indicated high cell survival more than 80% and no skin irritation. In addition, the results showed that calcium and phosphorous were preferentially attached to the composite hydrogel surface to grow apatite crystal (Ca/P ratio 1.86) compared to attaching to the chitosan hydrogel (Ca/P ratio 1.48) in 21 days of testing.

Synthesis and evaluation of wound healing properties of hydro-diab hydrogel loaded with green-synthetized AGNPS: in vitro and in ex vivo studies

In diabetic patients, the presence of neuropathy, peripheral vascular diseases and ischemia, leads to the formation of foot ulcerations with a higher risk of infection because the normal response to bacterial infection is missing. In the aim to control and treat diabetic foot ulcerations (DFUs), wound dressings that are able to absorb exudate, to prevent infections, and to promote wound healing are needed. For this reason, the aim of the present research was to synthetize a biocompatible hydrogel (called HyDrO-DiAb) composed of carboxymethylcellulose loaded with silver nanoparticles (AgNPs) for the treatment of diabetic foot ulcers. In this study, AgNPs were obtained by a green synthesis and, then, were dissolved in a CMC hydrogel that, after a freeze drying process, becomes a flexible and porous structure. The in vitro and in ex vivo wound healing activity of the obtained HyDrO-DiAb hydrogel was evaluated.

Formaldehyde and tripolyphosphate crosslinked chitosan hydrogels: Synthesis, characterization and modeling

In this work, the synthesis of crosslinked chitosan hydrogels was performed by ionic and covalent interactions using tripolyphosphate (TPP) and formaldehyde (CH₂O), respectively. The hydrogels synthesis was performed using a D-Optimal combined experiment design with two mixing variables, A and B representing the TPP weight fraction (slack variable) and CH₂O weight fraction, respectively, and three (3) process variables C-chitosan concentration, D-cross-linker concentration, and E-Contact time. The response variables studied were the point of zero charge (pH_PZC), the swelling ratio (SW), and the equilibrium water content (EWC), which are relevant physicochemical properties in applications such as the pollutant removal from water. According to the ANOVA results, the model obtained was significant; this means it can be adequately used to predicting pH_PZC, SW, and EWC from the mixing and process variables, obtaining coefficients of determination R² of 0.9572, 0.8900, and 0.8447, respectively. The pH_PZC is affected by chitosan concentration, while the crosslinker concentration influences the SW, and the contact time most significantly affected the EWC. Morphology and hardness tests, thermal stability, infrared spectroscopy, and scanning electron microscopy, allowed verifying the types of crosslinking of chitosan with TPP and CH₂O.

Oral delivery of self-assembling bioactive peptides to target gastrointestinal tract disease

Peptides are known for their diverse bioactivities including antioxidant, antimicrobial, and anticancer activity, all three of which are potentially useful in treating colon-associated diseases. Beside their capability to stimulate positive health effects once released in the body, peptides are able to form useful nanostructures such as hydrogels. Combining peptide bioactivity and peptide gel-forming potentials can create interesting systems that can be used for oral delivery. This combination, acting as a two-in-one system, has the potential to avoid the need for delicate entrapment of a drug or natural bioactive compound. We here review the context and research progress, to date, in this area.

Preparation and Swelling Behaviors of High-Strength Hemicellulose-g-Polydopamine Composite Hydrogels

Hemicellulose-based composite hydrogels were successfully prepared by adding polydopamine (PDA) microspheres as reinforcing agents. The effects of PDA microsphere size, dosage, and nitrogen content in hydrogel on the mechanical and rheological properties was studied. The compressive strength of hydrogel was increased from 0.11 to 0.30 MPa. The storage modulus G’ was increased from 7.9 to 22.0 KPa. The gaps in the hemicellulose network are filled with PDA microspheres. There is also chemical cross-linking between them. These gaps increased the density of the hydrogel network structure. It also has good water retention and pH sensitivity. The maximum cumulative release rate of methylene blue was 62.82%. The results showed that the release behavior of hydrogel was pH-responsive, which was beneficial to realizing targeted and controlling drug release.

Biosourced Polysaccharide-Based Superabsorbents

In the last decades, many studies have been conducted on new materials to meet a growing industrial demand and to move scientific research forward. Superabsorbents are good examples of materials that have generated special attention in many fields for their ability to absorb and retain water up to 1000 times of their dry weight. They found many applications in hygiene products and other products, for a fast growing market of USD 9.58 Billion in 2019. Most of them are composed of synthetic polymers, which are often not environmentally friendly. Therefore, natural superabsorbents and particularly those based on polysaccharides have received a recent increased interest for their biodegradability, biocompatibility, and renewability. This review focuses on polysaccharide-based superabsorbents, on their properties, synthesis methods, and characterization. Their potential applications in many fields, such as biomedical and hygiene, agriculture, water treatment, and the building sector, are also reported with an interest in products already marketed.

The functions of hydrophobic elastic polyurethane combined with an antibacterial triclosan derivative in the dentin restoration interface

Dentin restoration produces weak interfaces because of the effects of bacterial microflora, biofilms, and mechanical, thermal, and shrinkage stresses. This results in secondary caries. Therefore, hydrophobic elastic polyurethane (PU) containing different concentrations of triclosan derivatives was synthesized and applied to solve this problem. The antibacterial PU was characterized according to its tensile strength (TS) and elasticity (ε) via a universal testing machine, and water sorption (Wsp) and solubility testing (Wsl) was performed according to ISO 4049: 2009. Additionally, this study evaluated the antibacterial properties of PU against Streptococcus mutans (ATCC35668) and Escherichia coli (ATCC25922). A marginal leakage test was performed to evaluate the leakage prevention property. As a result, the antibacterial PU showed high TS (>17 MPa), high elasticity (ε > 65%), and low Wsp (>81.06 μg/mm³) and Wsl (>11.22 μg/mm³). The PU exhibited antibacterial effects against both Streptococcus mutans and Escherichia coli. The antibacterial rates were over 90% and >99% for the 3% and 5% groups, respectively. Moreover, the marginal level of leakage was 0. Based on the mechanical properties, Wsp and Wsl values and the antibacterial properties, the 3% group exhibited satisfactory performance and has been deemed a possible solution to reduce the occurrence of secondary caries.

The Investigation of LRP5-Loaded Composite with Sustained Release Behavior and Its Application in Bone Repair

Low-density lipoprotein receptor-related protein 5 (LRP5) plays a vital role in bone formation and regeneration. In this study, we developed an injectable and sustained-release composite loading LRP5 which could gelatinize in situ. The sustained release of the composite and its efficacy in bone regeneration were evaluated. Sodium alginate, collagen, hydroxyapatite, and LRP5 formed the composite LRP5-Alg/Col/HA. It was found that the initial setting time and final setting time of LRP5-Alg/Col/HA containing 4% alginate were suitable for surgical operation. When the composite was loaded with 40 μg/mL LRP5, LRP5-Alg/Col/HA did not exhibit a burst-release behavior and could sustainably release LRP5 up to 21 days. Up to 18 days, LRP5 released from LRP5-Alg/Col/HA still present the binding activity with DKK1 (Wnt signaling pathway antagonist) and could increase the downstream β-catenin mRNA in bone marrow mesenchymal stem cells. Moreover, LRP5-Alg/Col/HA was found to significantly increase bone mineral density in the defect area after 6 weeks’ implantation of LRP5-Alg/Col/HA into the rats’ calvarial defect area. H&E staining detection demonstrated that LRP5-Alg/Col/HA could mediate the formation of a new bone tissue. Therefore, we concluded that Alg/Col/HA was a suitable sustained-release carrier for LRP5 and LRP5-Alg/Col/HA had a significant effect on repairing bone defects and could be a good bone regeneration material.

Biomolecule-Responsive Hydrogels in Medicine

Recent advances and applications of biomolecule-responsive hydrogels, namely, glucose-responsive hydrogels, protein-responsive hydrogels, and nucleic-acid-responsive hydrogels are highlighted. However, achieving the ultimate purpose of using biomolecule-responsive hydrogels in preclinical and clinical areas is still at the very early stage and calls for more novel designing concepts and advance ideas. On the way toward the real/clinical application of biomolecule-responsive hydrogels, plenty of factors should be extensively studied and examined under both in vitro and in vivo conditions. For example, biocompatibility, biointegration, and toxicity of biomolecule-responsive hydrogels should be carefully evaluated. From the living body's point of view, biocompatibility is seriously depended on the interactions at the tissue/polymer interface. These interactions are influenced by physical nature, chemical structure, surface properties, and degradation of the materials. In addition, the developments of advanced hydrogels with tunable biological and mechanical properties which cause no/low side effects are of great importance.

Multi-polysaccharide based stimuli responsive polymeric network for the in vitro release of 5-fluorouracil and levamisole hydrochloride

A three-polysaccharide-based core shell system is reported for the first time for the delivery of dual drugs.

Investigation on pH-switchable (itaconic acid/ethylene glycol/acrylic acid) based polymeric biocompatible hydrogel

A new variety of pH-sensitive polymeric hydrogels (IAE) have been developed and evaluated as biocompatible hydrogels using synergetic combinations of itaconic acid (IA), acrylic acid (AA), and ethylene glycol (EG) in water medium by free radical polymerization.